The invention generally relates to semiconductor manufacturing and integrated circuits and, more particularly, to silicon-controlled rectifiers, electrostatic discharge circuits, and methods of fabricating a silicon-controlled rectifier for use in an electrostatic discharge circuit.
An integrated circuit may be exposed to electrostatic discharge (ESD) events that can direct potentially large and damaging ESD currents to the integrated circuits of the chip. An ESD event involves an electrical discharge from a source, such as the human body or a metallic object, over a short duration and can deliver a large amount of current to the integrated circuit. An integrated circuit may be protected from ESD events by, for example, incorporating an ESD protection circuit into the chip. Upon the occurrence of an ESD event, the ESD protection circuit triggers a power clamp device to enter a low-impedance, conductive state that provides a path directing the ESD current to ground and away from the integrated circuit. The ESD protection device holds the power clamp device in its conductive state until the ESD current dissipates and the ESD voltage is discharged to acceptable levels.
A silicon-controlled rectifier (SCR) is a multiple-layer solid state device frequently utilized as a power clamp device in ESD protection circuits. In its high-impedance state, the silicon-controlled rectifier restricts current conduction to leakage current. However, a triggering signal can switch the silicon-controlled rectifier to a low-impedance state such that current is conducted between its anode and cathode. After the triggering signal is removed, the SCR remains in its low impedance state so long as the conducted current from the ESD event exceeds a holding current. When the conducted current drops below the holding current, the SCR returns to its high-impedance state.
Improved silicon-controlled rectifiers, electrostatic discharge circuits, and methods of fabricating a silicon-controlled rectifier for use in an electrostatic discharge circuit are needed.